The present invention relates to poly(trimethylene terephthalate) copolymer (hereinafter poly(trimethylene terephthalate) is referred to as PTT), a method for producing the same, a fiber using the same and a fibrous product thereof. More specifically, it relates to PTT copolymer high in molecular weight to be a material for a PTT fiber dyeable with cationic dye, a method for producing the same, a fiber using the same and a fibrous product thereof.
Even more specifically, the invention relates to PTT copolymer capable of being produced at a high solid-state polymerization rate and having a small loss in melting viscosity, which is excellent in hue and high in molecular weight as a material for PTT fiber dyeable with cationic dye, a PTT fiber dyeable with a cationic dye excellent in processability and high in toughness, which does not shrink much during dyeing or heat-setting, and a fibrous product thereof.
PTT fiber obtained by melt-spinning polycondensate of terephthalic acid or lower alcohol ester of terephthalic acid and 1,3-propanediol (also referred to as trimethylene glycol) is excellent in touch of soft feeling, drapability and stretchability and is superior in low-temperature dyeability and weather resistance. These qualities have never been seen in an existing synthetic fiber such as poly(ethylene terephthalate) fiber (poly(ethylene terephthalate) is hereinafter referred to as PET) or nylon 6 fiber.
The applicant of this patent application has overcome various problems relating to the development of PTT and PTT fiber and the processing thereof, and has recently marketed a PTT fiber (trade name: Solo Fiber) for the first time in the world.
The PTT fiber could be more widely used by combining it with other fiber material or being post-treated. According to the prior art PTT fiber, however, problems relating the dyeing may occur if the mating fiber to be combined therewith or the processing technique is unsuitable. For example, as the PTT fiber is dyeable substantially solely with a disperse dye, the disperse dye is liable to migrate to the polyurethane elastomeric yarn or resin having a coarse structure to deteriorate a color fastness such as wash-fastness, sweat-fastness or dry cleaning-fastness when the PTT fiber is combined with a polyurethane elastomeric yarn or the fabric of the PTT fiber is treated with polyurethane resin.
To solve the above problems, if the PTT fiber is modified to be dyeable with cationic dye, the cationic dye is ionic-bonded with a sulfonate which is a dyeing seat introduced into PTT, whereby the above-mentioned migration of dye does not occur to result in a high color fastness. Also, there is a characteristic that the clarity of the dyed fabric becomes higher.
The present inventors have already proposed a PTT fiber dyeable with cationic dye (hereinafter referred to as a CD-PTT fiber) for the purpose of further facilitating the excellent features of the PTT fiber while solving the above-mentioned problems regarding the dyeing (WO99/09238). According to this technology, CD-PTT and a CD-PTT fiber formed thereof are provided by esterification-reacting terephthalic acid which is a dicarbonic acid component and/or lower alcohol ester of terephthalic acid, typically dimethyl terephthalate, with 1,3-propanediol which is a diol component, and adding an ester-forming metallic salt of sulfonic acid which is a dyeing seat for cationic dye. Although this technology provides the PTT dyeable with cationic dye, which has been difficult in the prior art, it is still insufficient in view of the industrial production. Also, although the CD-PTT obtained by the above-mentioned technology is excellent in whiteness, this is still unsatisfactory in a use in which whiteness or strength at a higher level is required.
On the other hand, regarding a PTT homopolymer (hereinafter referred to as a homo PTT) other than CD-PTT, Japanese Unexamined Patent Publication No. 8-311177 (Kokai) discloses a method for obtaining a PTT having a b value of 10 or less and a content of oligomer of 1 wt % or less by esterification-reacting 1,3-propanediol with a terephthalic acid component, polycondensating an esterification-reaction product thus obtained to result in a prepolymer having an intrinsic viscosity in a range from 0.7 to 0.8, and polycondensating, in a solid state, the prepolymer thus obtained at a temperature in a range from 190 to 210xc2x0 C. to result in an intrinsic viscosity of 0.9 or more. Also, Japanese Unexamined Patent Publication (Kokai) No. 2000-159876, disclose a polymerization technology providing a homo PTT excellent in solid-state polymerization speed and melting stability by combining a titanium catalyst with a magnesium catalyst.
However, there are neither a description nor a suggestion, in these publications, regarding the CD-PTT or the significance of the copolymerization of ester-forming metallic salt of sulfonic acid. Particularly, since the melting stability becomes worse in comparison with homo PTT, as described later, when an ester-forming metallic salt of sulfonic acid is used as a copolymerization component, the same effect would not be expected even if the technology used for the homo PTT is applied as it is to the CD-PTT. In the above publication, however, there is neither a description nor a suggestion of the solution thereto. The homo PTT described in either of these publications is unsatisfactory in whiteness. Particularly, according to Japanese Unexamined Patent Publication (Kokai) No. 2000-159876, since a magnesium catalyst is combinatorily used for the polymerization, the L value (brightness) of the polymer becomes less than 70 to result in a blackish polymer, and this technology is not applicable to a CD-PTT requiring a clear color.
Known CD-PTT fibers have problems to be solved similar to CD-PTT. That is, the known CD-PTT fibers are problematic in that 1) since they are formed of a polymer of a low molecular weight, a toughness (the toughness is a fiber stiffness usually represented by the product of a fiber strength and a square root of a fiber elongation) causes a fabric to be easily broken, and 2) as they are excessively drawn in spite of their low molecular weight, the orientation of molecules in an amorphous region is liable to relax by heat during the dyeing or heat-setting process to cause a large fiber shrinkage, which results in a harsh feeling of hand touch of a fabric, and it is difficult that the fabric develops adequately a soft feeling.
The present inventors have found the following problems by diligently studying the polymerization or spinning technology of CD-PTT.
In the melt-spinning process of CD-PTT, as metallic salts of sulfonic acid copolymerized with each other are ionically crosslinked in a melting state, the melting viscosity significantly rises. Thereby, the removal of 1,3-propanediol is inhibited at a polycondensating reaction stage to result in a problem that it is difficult to increase the degree of polymerization. In addition, as CD-PTT has a lower thermal stability in comparison with PET, poly(buthylene terephthalate) or homo PTT, which have similar structures thereto, the molecular weight thereof does not rise even if the polycondensation time is prolonged but the depolymerization occurs due to the heat decomposition before the molecular weight reaches a level necessary for forming fibers, which yellows the polymer itself, and a high-molecular weight CD-PTT is not obtainable.
The present inventors have studied a high-molecular weight CD-PTT and succeeded in obtaining a CD-PTT having a high molecular weight, not achievable through the melt-spinning method, by once preparing a low-molecular weight CD-PTT (hereinafter referred to as a prepolymer) and polymerizing the same in a solid state. As a result of specifically studying the melt-spinning characteristic, hue and solid-state polymerization characteristic, however, the following problems have been found when this technology is carried out on an industrial scale.
That is, if characteristics such as an amount of terminal carboxyl groups of the prepolymer obtained through the melt-polymerization are outside a certain range, the solid-state polymerization speed, the melting stability or hue of the high-molecular weight CD-PTT thus obtained largely deteriorates. Particularly, the amount of terminal carboxyl groups is deeply related to copolymerization ratios, catalysts, additives and conditions of polycondensating reaction. Accordingly, the present inventors have newly found that these factors must be precisely controlled to obtain the high-molecular weight CD-PTT which is the object of the present invention.
On the other hand, although the tensile strength can be increased to a relatively high level by applying a high draw ratio to melt-spun fibers formed of the low-molecular weight CD-PTT, the fiber shrinkage becomes higher because the molecules are excessively stretched for the purpose of facilitating the tensile strength. When a fabric formed of such high-shrinkage fibers is subjected to a subsequent processing such as a dyeing, the fiber largely shrinks to make the fabric harsh to the hand, which is opposite to the soft feeling of hand touch expected from a low elastic modulus of PTT.
Such a phenomenon does not occur in a PET fiber having a structure similar to PTT. This is because, as PTT has a spiral molecular structure, even if the molecule of the PTT fiber is forcibly stretched, an amorphous region thereof largely shrinks when heated so that the molecular structure returns to the original stable spiral structure, resulting in the large shrinkage of the fiber. On the contrary, a molecular structure of PET is liable to have an irreversible stretched structure. While a soft feeling of hand touch could be obtained by suitably controlling the shrinkage, the weaving or knitting density must be extremely low in such a case when the fabric is prepared, which is very difficult in design.
A first problem of the present invention is to provide a high-molecular weight PTT copolymer suitable for material of a PTT fiber dyeable with cationic dye and excellent in hue, which is produced by the solid-state polymerization at a high speed and at a small decline of melting viscosity, and a method for producing the same.
A second problem of the present invention is to provide a PTT dyeable with cationic dye high, in toughness and excellent in processability, which does not largely shrink during the dyeing or heat-setting process, and a method for producing the same.
The present inventors have specifically studied the melt-polymerization characteristic and the solid-state polymerization characteristic of CD-PTT and found that the above-mentioned problems can be solved by controlling an amount of terminal carboxyl groups at a final stage of the melt-polymerization while using an ester-forming metallic salt of sulfonic acid which prepares dyeing seats for cationic dye. Further, the present inventors have found the necessary conditions for achieving the dyeability and color fastness for cationic dye, based on which the inventive CD-PTT is obtained.
The present inventors have found that the inventive PTT fiber high in toughness, low in shrinkage during the dyeing or heat-setting process as well as being excellent in processability is obtainable by extruding CD-PTT, having a high polymerization degree in a certain range, uniformly from a spinneret having a surface temperature and an atmospheric temperature in a certain range to result in an undrawn yarn low in orientation and crystallization and good in drawability which is then drawn at a ratio in a certain range.
That is, the present invention is as follows:
1. A PTT copolymer characterized in that it satisfies the following conditions (1) to (4):
(1) ester-forming sulfonate in a range from 0.5 to 5 mol % is copolymerized relative to a total dicarbonic acid component.
(2) bis (3-hydroxypropyl) ether in a range from 0.1 to 2.5 wt % is copolymerized;
(3) an intrinsic viscosity is in a range from 0.65 to 1.5 dl/g, and
(4) an amount of terminal carboxyl groups is 25 milli-equivalent per kg resin or less.
2. A PTT copolymer as defined by the above item 1 wherein the intrinsic viscosity is in a range from 0.85 to 1.25 dl/g.
3. A PTT copolymer as defined by the above item 1 wherein a b* value is in a range from xe2x88x922 to 6.
4. A method for producing a PTT copolymer characterized in that the method comprises the steps of: reacting lower alcohol ester of terephthalic acid, which is a main dicarboxylic acid component, with 1,3-propanediol, which is a main diol component, to form 1,3-propanediol ester of terephthalic acid and/or oligomer thereof; after completing the polycondensation reaction, once solidifying the resultant polymer; and heating the polymer in a solid state to increase an intrinsic viscosity thereof by 0.1 dl/g or more from that at a time when the polycondensation reaction has completed, and the method satisfies the following conditions (a) and (b):
(a) ester-forming sulfonate corresponding to an amount in a range from 0.5 to 5 mol % of a total dicarbonic acid component is added at any optional stage from the initiation of reaction to the completion of the polycondensation reaction, and
(b) an amount of terminal carboxyl groups of PTT copolymer is in a range from 5 to 40 milli-equivalent per kg resin before the initiation of solid-state polymerization.
5. A method for producing a PTT copolymer characterized in that the method comprises the steps of: reacting terephthalic acid, which is a main dicarboxylic acid component, with 1,3-propanediol, which is a main diol component, to form 1,3-propanediol ester of terephthalic acid and/or oligomer thereof; after completing the polycondensation reaction, solidifying the resultant polymer; and heating the polymer in a solid state to increase an intrinsic viscosity thereof by 0.1 dl/g or more from that at a time when the polycondensation reaction has completed, and the method satisfies the following conditions (a) to (c):
(a) the molar ratio of 1,3-propanediol to terephthalic acid is in a range from 0.8 to 2.5,
(b) in the reaction of terephthalic acid with diol mainly composed of 1,3-propanediol, at a stage wherein a rate of reaction of terephthalic acid is in a range from 75 to 100%, an amount of ester-forming sulfonate corresponding to a range from 0.5 to 5 mol % of total dicarboxylic acid component is added, and
(c) the amount of terminal carboxyl groups of PTT copolymer is in a range from 5 to 40 milli-equivalent per kg resin before the initiation of solid-state polymerization.
6. A method for producing a PTT copolymer comprising the steps of: by reacting terephthalic acid, which is a main dicarboxylic acid component, with 1,3-propanediol, which is a main diol component, to form 1,3-propanediol ester of terephthalic acid and/or oligomer thereof; after completing the polycondensation reaction, characterized in that the method satisfies the following conditions (a) to (c):
(a) a molar ratio of 1,3-propanediol to terephthalic acid is in a range from 0.8 to 2.5,
(b) in the reaction of terephthalic acid with diol mainly composed of 1,3-propanediol, at a stage wherein a rate of reaction of terephthalic acid is in a range from 75 to 100%, an amount of ester-forming sulfonate corresponding to a range from 0.5 to 5 mol % of total dicarboxylic acid component is added, and
(c) an amount of terminal carboxyl groups of PTT copolymer is in a range from 5 to 40 milli-equivalent per kg resin.
7. A method for producing a PTT copolymer as defined by any one of the above items 4 to 6, wherein an alkaline metal compound and/or an alkaline earth metal compound corresponding to an amount in a range from 1 to 100 mol % of ester-forming sulfonate is added at any optional stage from the initiation of reaction to the completion of the polycondensation reaction.
8. A PTT copolymer fiber characterized in that it satisfies the following conditions (1) to (4):
(1) ester-forming sulfonate in a range from 0.5 to 5 mol % is copolymerized relative to a total dicarboxylic acid component.
(2) bis (3-hydroxypropyl) ether in a range from 0.1 to 2.5 wt % is copolymerized;
(3) an intrinsic viscosity is in a range from 0.65 to 1.5 dl/g, and
(4) an amount of terminal carboxyl groups is in a range from 5 to 40 milli-equivalent per kg fiber or less.
9. A PTT copolymer fiber characterized in that ester-forming sulfonate in a range from 0.5 to 5 mol % is copolymerized relative to a total dicarboxylic acid component, and the fiber satisfies the following conditions (A) to (C):
(A) an intrinsic viscosity [xcex7] is in a range from 0.65 to 1.4 dl/g,
(B) a peak temperature of a dynamic loss tangent is in a range from 105 to 140xc2x0 C., and
(C) a boiling water shrinkage is in a range from 0 to 16%.
10. A PTT copolymer fiber as defined by the above item 9, further satisfying the following conditions (D) and (E):
(D) an elongation at break is in a range from 20 to 70%, and
(E) a toughness is 16 or more, wherein the toughness is calculated by the following equation:
Toughness=[Strength (cN/dtex)]xc3x97[Elongation (%)]xc2xd. 
11. A PTT copolymer fiber as defined by the above item 10, wherein the toughness is 17.5 or more.
12. An undrawn PTT copolymer fiber characterized in that it consists of PTT formed by copolymerizing ester-forming sulfonate in a range from 0.5 to 5 mol % to a total dicarboxylic acid component to have an intrinsic viscosity in a range from 0.65 to 1.4 dl/g, and it has an elongation at break in a range from 150 to 600% and a crystallization peak temperature in a range from 64 to 80xc2x0 C.
13. A method for producing a PTT copolymer fiber characterized in that an undrawn PTT copolymer fiber, having an elongation at break in a range from 150 to 600% and a crystallization peak temperature in a range from 64 to 80xc2x0 C., is drawn at a draw ratio in a range from 30 to 99% of the maximum draw ratio, and the undrawn PTT copolymer fiber consists of PTT formed by copolymerizing ester-forming sulfonate in a range from 0.5 to 5 mol % to a total dicarboxylic acid component to have an intrinsic viscosity in a range from 0.65 to 1.5 dl/g.
14. A method for producing a PTT copolymer fiber characterized in that the PTT is formed by copolymerizing ester-forming sulfonate in a range from 0.5 to 5 mol % to a total dicarboxylic acid component to have an intrinsic viscosity in a range from 0.65 to 1.5 dl/g, the PTT is extruded from a spinneret having a surface temperature in a range from 250 to 295xc2x0 C. and, after being cooled and solidified, is taken up at a speed in a range from 100 to 3,000 m/min to be an undrawn yarn which is then drawn at a temperature in a range from 30 to 90xc2x0 C. and a draw ratio which is in a range from 30 to 99% of the maximum draw ratio and, then a drawn fiber obtained is heat-treated at a temperature from 100 to 200xc2x0 C.
15. A method for producing a PTT copolymer fiber as defined by the above item 14, wherein the PTT is extruded from a spinneret with a heating tube having a length in a range from 20 to 500 mm and heated at a temperature in a range from 150 to 350xc2x0 C.
16. A method for producing a PTT copolymer fiber as defined by any one of the above items 13 to 15, wherein the undrawn fiber is once wound as a package and then drawn.
17. A method for producing a PTT copolymer fiber as defined by any one of the above items 13 to 15, wherein the undrawn fiber is not wound as a package but is continuously drawn.
18. A staple fiber obtained from the PTT copolymer fiber as defined by any one of the above items 8 to 10, wherein the fiber length is in a range from 3 to 300 mm and a degree of crimp is 5% or more.
19. A fiber product in which the PTT copolymer fiber as defined by any one of the above items 8 to 10 is partially or wholly used.
20. A fiber product in which the staple fiber as defined by the above item 18 is partially or wholly used.